Ballistic resistant articles which contain high strength fibers for use as structural members and panels for a wide variety of military equipment are known. Recently, one of us developed ballistic resistant materials which are fire-resistant, smoke resistant, non-toxic, non-conductive, self-supporting and stiff, machineable, thick and strong so as to allow their use in structural armor applications and as ballistic resistant liners.
First, a prepreg that can be easily handled is formed. The prepreg is formed by coating high strength magnesia aluminosilicate glass fibers with a solution of a partially condensed, further condensable low molecular weight phenol formaldehyde resole reaction product and evaporating the solvent from the solution. The coated fibers then are heated to increase the resole molecular weight and thereby form the easily handleable prepreg. Prepreg plies are then molded by heating under pressure until by-product water gradually escapes. Then they are heated to an elevated temperature and held at that temperature to fully polycondense and cure the resin. A plurality plies of such prepregs will be molded to form the ballistic composites.
These recent improvements were obtained with solutions containing large amount of solvents; i.e., 25% alcohol, 10% water and excess formaldehyde. See U.S. Pat. No. 4,842,923 issued in 1989.